The present invention relates to automotive internal combustion engines and, more specifically, to an automotive internal combustion engine of the particular nature having mixture control means adapted to regulate the concentration of fuel or, more exactly, the ratio between the air and fuel components in the air-fuel mixture to be supplied to the engine cylinders through detection of the concentration of any of the chemical components in the exhaust gases being emitted from the engine. The chemical component whose concentration is to be detected may be the oxygen, hydrocarbon, carbon monoxide or dioxide or nitrogen oxide component in the exhaust gases although the oxygen component in particular is usually preferred for ease of detection and accuracy in approximating therefrom the proportions of the various components of the exhaust gases. An analog signal proportional or otherwise representative of the detected concentration is supplied to a computing circuit which is arranged to produce an output signal, usually of a pulse form, for controlling the mixture supply system (which may be a carburetor or of the fuel injection type) of the engine in such a manner that the air-to-fuel ratio of the mixture to be produced in the system is maintained within a predetermined range.
Apart from this, some modernized automotive vehicles are equipeed with catalytic reactors in the exhaust systems of the engines. The catalytic reactor is reactive to a predetermined kind or predetermined kinds of toxic, air contaminative compounds such as hydrocarbons, carbon monoxide and nitrogen oxides in the exhaust gases for converting such compounds into harmless substances before the exhaust gases are discharged to the open air. The above described mixture control means is useful especially when combined, in effect, with the catalytic reactor of this character because the reactor will be enabled to best exhibit its potential function if the mixture control means is arranged in such a manner that the air-to-fuel ratio of the mixture produced in the mixture supply system of the engine is regulated toward a certain value optimum for the performance characteristics of the reactor or maintained within a predetermined range containing such a value. If, for example, catalytic reactor is of the ternary type which is capable of concurrently processing the above-mentioned three kinds of contaminants, viz., hydrocarbons, carbon monoxide and nitrogen oxides in the exhaust gases, it is advantageous that the mixture control means be arranged so that the air-to-fuel ratio of the mixture is regulated toward a stoichiometric ratio of approximately 14.8:1 or maintained with a predetermined range containing the stoichiometric ratio. This is because of the fact that it is the stoichiometric mixture which enables the ternary type catalytic reactor to achieve its maximum conversion efficiency, as is well known in the art.
As is also well known in the art,. the air-to-fuel ratio of the mixture supplied to the engine cylinders is predominant over the power output and the fuel consumption rate of the engine. If, thus, the air-to-fuel ratio of the mixture to be supplied to the engine cylinders is controlled without respect to the varying operational conditions of the engine, then the engine will fail to operate properly throughout the various modes of operation, especially during high load operating conditions. Such a problem will arise not only when the mixture control means is used in combination with a catalytic reactor of any type but when the control means is provided in an internal combustion engine which is void of such a reactor because, in whichsoever case, the control means is so arranged as to control the air-to-fuel ratio of the mixture virtually regardless of the actual operating conditions of the engine. The present invention contemplates provision of a useful, simple and economically readily feasible solution to this problem.